Did I buy the wrong mount?!? More Trig / idiot content…

Continuing my Ragley Trig build, I bought a couple of 160mm flat mount to post mount caliper adaptors

front went on fine, lovely

the back, however, I can’t get the mount to sit flat on the frame as the caliper and mount want to sit against the frame with the mounting holes between frame and adaptor not lining up

can anyone see the (probably) obvious issue that I’m missing?!

I think you’ve got the right mount, they just don’t work with a lot of (most?) frames for the reason you have found. I had this problem and ended up just buying a flat mount caliper 🙁

As above really. There wasn’t much space above the calliper on my Trig and that was flat mount on an XL frame.

I don’t know if it’s any help, but Merlin have some TRP flat mount to post mount adapters. The 160mm looks the same as yours and too big, but the 140mm is shallower (no guarantee it’ll fit though).

If you can live with 140mm at the rear it might be an option.

https://www.merlincycles.com/trp-flat-mount-to-post-disc-brake-adaptor-89957.html

It looks like adaptor and frame space issue, not wrong adapter.

Can I ask: what advantage did flat mount bring over post mount?

Can I ask: what advantage did flat mount bring over post mount?

One minor thing is that it lowers production cost as it moves the threads to the caliper, rather than the frame. It also means a bodged installation only writes off a caliper instead of the more expensive part.

It also makes the frames very slightly lighter.

Only benefit I can see is that flat mount fits in a smaller space. Not that that helps the OP out much.

PITA to be honest, another change in standard we didn’t need.